Biomedical subjects
A Packer
Publications and source records attributed to A Packer.
Soil pathogens and spatial patterns of seedling mortality in a temperate tree.
The Janzen-Connell hypothesis proposes that host-specific, distance- and/or density-dependent predators and herbivores maintain high tree diversity in tropical forests. Negative feedback between plant and soil communities could be a more effective mechanism promoting species coexistence because soil pathogens can increase rapidly in the presence of their host, causing conditions unfavourable for local conspecific recruitment. Here we show that a soil pathogen leads to patterns of seedling mortality in a temperate tree (Prunus serotina) as predicted by the Janzen-Connell hypothesis. In the field, the mean distance to parent of seedling cohorts shifted away from maternal trees over a period of 3 years. Seedlings were grown in soil collected 0-5 m or 25-30 m from Prunus trees. Sterilization of soil collected beneath trees improved seedling survival relative to unsterilized soil, whereas sterilization of distant soil did not affect survival. Pythium spp., isolated from roots of dying seedlings and used to inoculate healthy seedlings, decreased survival by 65% relative to controls. Our results provide the most complete evidence that native pathogens influence tree distributions, as predicted by the Janzen-Connell hypothesis, and suggest that similar ecological mechanisms operate in tropical and temperate forests.
Comorbidity, nutritional intake, social support, weight, and functional status over time in older cancer patients receiving radiotherapy.
It is essential that nurses gain insight about the responses of older adults to standard anticancer therapies because there is ongoing concern about whether the elderly are affected adversely by the prescribed therapy. The purpose of this longitudinal prospective study was to describe selected outcomes and their relationships in a sample of 45 elderly (mean age 69.8 years; range 61-86) patients receiving radiotherapy for either breast (42%) or lung (58%) cancer. The outcome variables were weight and multidimensional functional status; moderator variables were co-morbidity, nutritional intake, estimated adequacy of intake, radiation dose, side effects, and social support. Data were collected at the beginning of radiation (T1), the middle of therapy (T2), the conclusion of therapy (T3), and three months post radiation (T4). Although 81.4% had some concurrent condition, those with a comorbid condition did not respond significantly differently from those without a comorbid condition on any of the major variables at any of the four times. At none of the four times was the caloric intake adequate to meet the estimated energy requirements for usual activity (range 67.9-71.5%). However, caloric intake was not significantly related to weight at any of the four times. There was a significant weight decrease from beginning of therapy to the middle of therapy and from the beginning of therapy to conclusion of therapy. The percentage of calories contributed by protein was significantly correlated with weight during radiotherapy, and protein calories consumed at the previous time were correlated with weight at T2 and T3. In contrast, the percentage of calories contributed by carbohydrate intake was significantly negatively correlated with two of the four functional status measures at each time, but was not related to weight. In addition carbohydrate calories consumed at the previous time also were related to one or more functional status measures at succeeding time points. Almost no relationships were found between social support and the outcome measures of weight and functional status. Scores on three of the four functional status measures suggest improvement over time from initiation of radiation to 3 months after therapy. Scores on the fourth measure, Overall Health Rating, suggest a slight decline; however, the average score reflects good overall health. These findings provide evidence that this group of elderly, the great majority of whom had at least one comorbid condition, tolerated the course of radiation with less than adequate intake for usual activity, a slight decrease in mean weight, but without major disruptions in functional status.(ABSTRACT TRUNCATED AT 400 WORDS)
A Rorschach analysis: parallel disturbance in thought and in self/object representation.
The relationship between thought process disturbance and the structure of internal object relations was investigated by comparing Rorschach Special Scorings and content variables that reflected developmental levels of object relations. Selected Special Scorings from the Comprehensive System (Exner, 1990) and composite (WSum6) scores were correlated with Urist's (1977) Mutuality of Autonomy Scale (MOA) on the Rorschach protocols of 35 borderlines, 15 schizophrenics, and 19 narcissists. Correlations between composite scores of severe thought process disturbance and severe imbalance in internalized object representations were highly significant, p < .0001. The hypothesis that there is a significant relationship between disturbance in internalized self/object differentiation and thought process disturbance was supported. Implications of this study are discussed as they relate to empirical validation of theoretical constructs concerning ego function deficit and self/object disturbance.
The kit-ligand (steel factor) and its receptor c-kit/W: pleiotropic roles in gametogenesis and melanogenesis.
The c-kit receptor tyrosine kinase belongs to the PDGF/CSF-1/c-kit receptor subfamily. The kit-ligand, KL, also called steel factor, is synthesized from two alternatively spliced mRNAs as transmembrane proteins that can either be proteolytically cleaved to produce soluble forms of KL or can function as cell-associated molecules. The c-kit receptor kinase and KL are encoded at the white spotting (W) and steel (Sl) loci of the mouse, respectively. Mutations at both the W and the Sl locus cause deficiencies in gametogenesis, melanogenesis and hematopoiesis. The c-kit receptor is expressed in the cellular targets of W and Sl mutations, while KL is expressed in their microenvironment. In melanogenesis, c-kit is expressed in melanoblasts from the time they leave the neural crest and expression continues during embryonic development and in the melanocytes of postnatal animals. In gametogenesis c-kit is expressed in primordial germ cells, in spermatogonia, and in primordial and growing oocytes, implying a role at three distinct stages of gametogenesis. Many mutant alleles are known at W and Sl loci and their phenotypes vary in the degree of severity in the different cellular targets of the mutations. While many W and Sl alleles severely affect primordial germ cells (PGC), several mild Sl alleles have weak effects on PGCs and exhibit differential male or female sterility. Steel Panda (Sl(pan)) is a KL expression mutation in which KL RNA transcript levels are reduced in most tissues analyzed. In female Sl(pan)/Sl(pan) mice, ovarian follicle development is arrested at the one layered cuboidal stage as a result of reduced KL expression in follicle cells, indicating a role for c-kit in oocyte growth. Wsh is a c-kit expression mutation, which affects mast cells and melanogenesis. While the mast cell defect results from lack of c-kit expression, the pigmentation deficiency appears to stem from ectopic c-kit receptor expression in the somitic dermatome at the time of migration of melanoblasts from the neural crest to the periphery. It is proposed that the ectopic c-kit expression in Wsh mice affects early melanogenesis in a dominant fashion. The "sash" or white belt of Wsh/+ animals and some other mutant mice is explained by the varying density of melanoblasts along the body axis of wild-type embryos.
Influence of age on problems experienced by patients with lung cancer undergoing radiation therapy.
The purpose of this prospective, longitudinal study was to determine if patients with lung cancer who are 65 years of age or older experience problems differently than do patients younger than age 65 during and following radiation treatment. The moderator and outcome variables selected for study were recognized attendant problems that may develop during lung cancer treatment and that may influence the treatment regimen and response. No statistically significant differences were found between patients age 65 or older and those younger than age 65 on caloric intake, adequacy of energy intake, total radiation dose, concurrent illnesses, and social support at any of four data-collection periods. Similarly, there were no significant differences on weight, body mass index, and multidimensional functional status. The relationship between the social support subscales and functional status measures for the 65-or-older group suggested that those subjects with lower social support perceived themselves to have better functional status. There was no relationship between social support and two functional status measures for the under-65 group. The significant relationships between social support and the overall health rating were in opposite directions for the two age groups. The results suggest that chronologic age alone may not be a sufficient criterion to determine therapeutic regimen or to suggest that unique problems may result.
Descemetocele formation in a patient with a postoperative corneal dellen.
Dellen formation generally follows localized evaporation and dehydration of the cornea. The condition follows a disruption in the ocular tear film and usually can be managed conservatively with lubricants. We recently treated a patient with a postoperative dellen that progressed to a descemetocele and required a patch graft to prevent perforation. Recognition of this potential complication emphasizes the need to begin treatment immediately after the onset of dellen.
[Relevant aspects of organizing electronic data processing services for data from population censuses and surveys in Latin America].
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Prescription patterns in outpatients.
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Contribution of generalized negative affect to elevated menstrual cycle symptom reporting.
We investigated women's belief that they suffered from premenstrual syndrome (PMS) by monitoring patterns of symptom reporting over a 5-week period in relation to the underlying trait of negative affect. We expected that women reporting high negative affect would be more likely to report menstrual cycle distress than those reporting low negative affect. One hundred twenty-one women rated the typical occurrence and severity of premenstrual changes on a retrospective questionnaire and then made daily ratings of their changes for the duration of one cycle. In addition, they completed a questionnaire measuring positive and negative affect. Data analysis revealed a clear subgroup whose retrospective reports of premenstrual change were not substantiated by the cycle of their daily ratings. Although this subgroup also reported more negative affect, the magnitude of the effect was relatively small. The possible contribution of both negative outlook and the meaning of the self-identified label of PMS are discussed.